11:10 〜 11:30
[AHW21-02] Use of the stream network controlled by groundwater seepage to constrain hydraulic properties at the catchment scale
★Invited Papers
キーワード：groundwater flow, seepage zones, stream network, model calibration, hydraulic properties
Predicting water flow and storage at catchment to regional scale is challenged by the lack of knowledge on subsurface structure and properties, specifically for ungauged basins.
Under the assumption that the perennial stream network is mostly fed by groundwaters, its spatial extent is controlled by the magnitude of the subsurface transmissivity (T), i.e. the product of the hydraulic conductivity (K) and the saturated aquifer thickness (dsat), with respect to the actual recharge rate (R). It is especially the case for shallow crystalline aquifers under temperate climates where the surface and subsurface hydrological systems are directly connected. Here we propose an inversion approach based on the spatial organization of the observed hydrographic network to constrain hydraulic properties of the aquifer.
Using a parsimonious 3D groundwater flow model in steady state, we propose a novel performance criterion to assess the similarity between the simulated seepage zones and the observed stream network. We investigate the sensitivity of our methodology to different digital elevation models (DEM) and stream network products from different databases that may impact the estimates through their different spatial resolutions. We use this method to determine the equivalent hydraulic conductivity for 24 crystalline catchments in western France.
The results show that our methodology allows predicting the spatial patterns of the stream network with a high sensitivity to the hydraulic conductivity. We found that estimated hydraulic conductivities vary over two orders of magnitude [10-5 to 10-4 m/s] across the 24 investigated catchments and are well correlated to the lithology. While the DEM resolution has no major effect on the results, we found that the proportion of described low-order streams significantly controls the estimations.
The proposed approach constitutes a paradigm shift in current methodologies designed to assess catchment-scale hydraulic properties with great perspectives regarding the emergence of remote sensing techniques for the mapping of wetlands and soil moisture. In perspective, this approach could be used in transient modeling simulating intermittent stream dynamics, which is also controlled by the aquifer storage capacity (S), i.e., the porosity. We expect that our method might bring up new opportunities to provide hydrological predictions such as hydrographic network dynamics in a changing climate.
Under the assumption that the perennial stream network is mostly fed by groundwaters, its spatial extent is controlled by the magnitude of the subsurface transmissivity (T), i.e. the product of the hydraulic conductivity (K) and the saturated aquifer thickness (dsat), with respect to the actual recharge rate (R). It is especially the case for shallow crystalline aquifers under temperate climates where the surface and subsurface hydrological systems are directly connected. Here we propose an inversion approach based on the spatial organization of the observed hydrographic network to constrain hydraulic properties of the aquifer.
Using a parsimonious 3D groundwater flow model in steady state, we propose a novel performance criterion to assess the similarity between the simulated seepage zones and the observed stream network. We investigate the sensitivity of our methodology to different digital elevation models (DEM) and stream network products from different databases that may impact the estimates through their different spatial resolutions. We use this method to determine the equivalent hydraulic conductivity for 24 crystalline catchments in western France.
The results show that our methodology allows predicting the spatial patterns of the stream network with a high sensitivity to the hydraulic conductivity. We found that estimated hydraulic conductivities vary over two orders of magnitude [10-5 to 10-4 m/s] across the 24 investigated catchments and are well correlated to the lithology. While the DEM resolution has no major effect on the results, we found that the proportion of described low-order streams significantly controls the estimations.
The proposed approach constitutes a paradigm shift in current methodologies designed to assess catchment-scale hydraulic properties with great perspectives regarding the emergence of remote sensing techniques for the mapping of wetlands and soil moisture. In perspective, this approach could be used in transient modeling simulating intermittent stream dynamics, which is also controlled by the aquifer storage capacity (S), i.e., the porosity. We expect that our method might bring up new opportunities to provide hydrological predictions such as hydrographic network dynamics in a changing climate.